A controller is provided for controlling an air conditioner installed in a facility such as a building. A single unit of such a controller, for example, is provided for each air conditioner. When multiple air conditioners coexist, multiple controllers are grouped and installed in a single control-unit control panel. In this case, space for installation of the controllers in the control panel is limited, and thus miniaturization of the controllers is required. A device in which printed circuit boards are overlapped and arranged is proposed in response to this requirement (for example, see Patent Literature 1). This device includes an opening for insertion and removal of the printer circuit board, and is configured to enable placement of the printed circuit board through the opening.